This invention relates to a clamp, particularly for securing a ruler to a guide.
When working with gypsum wall board panels, it is frequently necessary to score a panel along a line that is accurately parallel to an edge of the panel. This can be done by measuring from the edge of the panel at two locations, marking the panel, setting a straight edge between the marks, and running a knife along the straight edge. However, this is a time consuming and inaccurate operation.
Various guide mechanisms have been proposed for facilitating scoring of wallboard. For example, Kaplan et al, U.S. Pat. No. 4,903,409, discloses a scoring tool which includes a guide that runs against the edge of the panel and a ruler that projects from the guide and overlies the surface of the panel. A knife is fitted to the ruler and is adjustable in position lengthwise of the ruler by releasing and engaging a clamp which receives a knife holder. Also, Peugh et al, U.S. Pat. No. 5,600,892, discloses a drywall panel cutter having a guide which engages the edge of the panel and a ruler which projects perpendicular to the guide and is moveable lengthwise by releasing and engaging a clamp. At one end, the ruler carries a tool for scoring the drywall panel.
The clamps used in wall board scoring and marking tools are generally unsatisfactory and do not hold the ruler firmly relative to the guide or hold the knife holder firmly relative to the ruler.